1993 520H - wiring for the R/R?

[seuadr 488]

Hey all - working on transplanting an older onan into my 520H. Down to a few pieces of wiring now and a couple questions. 

 

In the demystified wiring schematic i see a white wire and a gray wire running from what i presume is the R/R.. but I don't have a white wire. Just a gray one (and the red one which i presume is for the starter)

 

Now, if i test continuity between that gray wire and the tach, i get it - so i think that checks out. I also have a white wire connected to a purple wire, but that runs down to the front of the tractor:

 

 

Now, that white wire seems to be in the right location to be the head temp, which seems to be where that purple is going.. 

 

But if the R/R runs to the tach, and the white wire is the head temp.. where is my R/R DC power wire??

[WHX?? 47,854]

Had to do that while I study it!

[WHX?? 47,854]

Colors may not be the same on the replacement motor. Since this may be true don't worry about keeping colors the same just their function.   Are you using a nine pin or just splicing? 

One of the outside pins of the RR should have a tach wire on it. Center terminal of RR  should connect to tractor side harness white. 

In other words whatever color wire is on the cyl temp switch just make sure that goes to the purple tractor side. Same with what ever color is on say the starter small terminal goes to light blue on the tractor side. So on and so forth. 

 

The red wire that goes through the engine connector does not have to be there that was always the trouble pin. It was just away for the man to get to the big cable (large terminal on starter) to the battery.  You can tie that right to battery positive. That wire carries the whole tractor load 

Edited April 5, 2021 by WHX24

[seuadr 488]

20 minutes ago, WHX24 said:

Colors may not be the same on the replacement motor. Since this may be true don't worry about keeping colors the same just their function.   Are you using a nine pin or just splicing? 

One of the outside pins of the RR should have a tach wire on it. Center terminal of RR  should connect to tractor side harness white. 

In other words whatever color wire is on the cyl temp switch just make sure that goes to the purple tractor side. Same with what ever color is on say the starter goes to light blue on the tractor side. 

Actually using the old harness, as everything until now has lined up great! The "new" R/R has a single line off it that is red from the b+ terminal. The old R/R also has a b+ terminal in the same location (honestly almost the exact same R/R) but it shows a white wire going from the b+ terminal on the old R/R that I don't see in the harness. The more i look at it, though, the more i think the red wire is supposed to be the white one. I traced it back in the harness far enough to find a whitewhite into the red with a butte connection.

 

That in turn goes to this relay which seems like the right combo of wires to be the starter relay?

 

 

It runs through a 30a blade fuse (single) so that seems to match. The purple and black from that relay go straight into the next relay. 

[seuadr 488]

I think part of the confusion on my side is no engine connector. These are all butte connected in a big mess.

[WHX?? 47,854]

3 minutes ago, seuadr said:

Actually using the old harness, 

Ahh that makes a little more sense. Looking at the rest of your wiring it appears it's been worked over before so now even more important you go somewhat color blind. You just don't know what a PO did in the way of switching up factory colors and splicing in God forsaken places then to add insult to injury cover the whole mess up with five rolls of black tape. Check his connections carefully, many time a PO uses a channel locks for a crimper you get my drift! 

Go by physically tracing wires out to be sure they go as should per the diagram. 

[seuadr 488]

40 minutes ago, WHX24 said:

 

In other words whatever color wire is on the cyl temp switch just make sure that goes to the purple tractor side. Same with what ever color is on say the starter small terminal goes to light blue on the tractor side. So on and so forth. 

 

The red wire that goes through the engine connector does not have to be there that was always the trouble pin. It was just away for the man to get to the big cable (large terminal on starter) to the battery.  You can tie that right to battery positive. That wire carries the whole tractor load 

So I don't have a temp sensor installation location on this motor - should i just hook up the sensor and tuck it up somewhere?

 

 

Looks like that red wire is gone if i am looking at this right - there is a push button that runs straight from the positive battery post to the starter. 

[WHX?? 47,854]

8 minutes ago, seuadr said:

hook up the sensor and tuck it up somewhere?

Its there a way you can get it in some cylinder fins somewher? Better than nothing I guess. 

 

10 minutes ago, seuadr said:

push button that runs straight from the positive battery post to the starter. 

I was wonder what that cobblement was! Looks like someone had ig switch problems and wasn't bright enough to just replace the switch?!?!?  Whatever works for ya i guess! 

[seuadr 488]

9 minutes ago, WHX24 said:

Its there a way you can get it in some cylinder fins somewher? Better than nothing I guess. 

Fun story - sensor is the same thread as the bolts that hold the tins on:

 

 

I can snug it right up into the head that way. Hole isn't as deep - but better than nothing?

[seuadr 488]

Oops. I guess this sensor is ready for retirement. 

Oh well, new motor, new sensor, right?! 🤣

 

[seuadr 488]

Gotta get a couple of those double pin connectors to piggy back the gray (now black, cause i don't have gray - but labeled!) On one of the AC pins and the b+ pin is ready to connect as well!

[seuadr 488]

That sensor is made of unobtanium, huh.

[WHX?? 47,854]

38 minutes ago, seuadr said:

That sensor is made of unobtanium, huh.

Nooo guys here should hve them ... put an ad in wanted .